Wait if the best way to earn money is 2*cost, then why is the average global sales price for Strawberry Bannana Smoothie 33$, when it costs 5$ to make it? Wouldn't the most poriftable be 10$?
Good question. This relates to the postulates I made going in: specifically, this assumes infinite supply, such as with the import market. When you have products without infinite supply (and, specifically, when you have someone attempting to sell a product they manufacture themselves), you will often not be able to maintain the manufacturing necessary to saturate the demand maximum.
Second, note that my analysis was from the perspective of the *retailer*. It may cost the manufacturer $5 to make that Strawberry Banana Smoothie, but if he sells his excess on B2B for, say, $200, whoever buys that smoothie to send it to retail will make the most money-per-tick from it by setting its price at $400. Contrary to what was suggested above, this is *independent* of quality, or any other factor... it is completely a function of the cost of the product to the retailer.
This is rather counter-intuitive, I know, and this is one of the less realistic aspects of the game engine. Scott currently has the price curve programmed identically for every product; at best, different products get different multipliers, but they still all have the same quantity = x/price^2 model, and that's the root fact that leads to the MAX(profit) = 2 * cost math.
I'd be happy to show some examples if you don't believe it, but what I'd recommend you try is a simple 2-tick test. Take a product from the import market, set the price at whatever you think should be right, see what your profit (not revenue, but profit: price - cost times units sold) is, and then try again with the 2 * cost, and see how it works out. (Note that because the game just carries over remainders, you probably need a product with a decent throughput to do a good test... trying it with low-volume products like refrigerators will need a really long time to compare.)